The widespread use of high energy lithium batteries has provided increased capabilities for portable and remotely deployed electronic packages. These advanced power sources have allowed vastly increased data gathering and transfer when compared to other conventional means. This is because of the benefits attained from the lithium sulphur dioxide balanced cell which higher cell operating voltage, exceptionally long field operation life, a higher energy density, lower temperature performance and superior shelf life.
One drawback, however, is that these superior power sources are relatively expensive. As a result, indiscriminate replacement of these batteries should be avoided when they still have considerable power in reserve. Usual practices call for the changing of many of the batteries at periodic intervals when high reliability is called for during field operations. Oftentimes however, partially discharged batteries would be more than adequate for additional use if their energy levels were known by operating personnel. Conventional testing techniques that may be adequate at a laboratory or depot simply do not lend themselves to field operations where such testing devices are bulky or where permanent installation generally is not feasible.
Thus the need exists in the state-of-the-art for a simple, easy to use, continuous monitor of lithium battery energy which is easily read, does not require appreciable operating energy, is conveniently packaged, is rugged and cost effective.